Improved liquid-liquid contacting process using di(beta-cyanoethyl)-amine



H. R. ANTLE IMPROVED LIQUID-LIQUID CONTACTING PROCESS oct.' 23, 1951 USING DI (BETACYANOETHYL)AMINE Filed Dec. 2l. 1948 Patented Oct. 23, 1951 IMPRGVED' LIQUID-LIQUID CONTACTING PROCESS USING DI(BETACYANOETHYL)- AMINE Herbert R. A-ntle, Bartlesville, Okla., assignor toy Phillips Petroleum Company, a. corporation of Delaware- Application December 21, 1948, Serial No. 66,556

6 Claims. 1

This invention relatesv to a solvent extractionl process'. In one of its more specic aspects' it relates to an extraction process in which asphal'tic materials' and color bodies' may be simultaneously extracted with the separation of one type of hydrocarbon compounds from a hydrocarbon mixture containingthese materials.

The use of. dilbet'a-cyanoethyD-amine as a selective solvent is known. It is also known that' this' solvent selectively dissolves' suchmaterials as* asphaltic materials and/or color-imparting materials from hydrocarbons'containing them. This solvent has' further application in theextraction of color bodies and/or asphaltic materials containing such hydrocarbon mixtures as crude oils), crude oill fractions, gas oils, and similar" hydrocarbonA products. My invention is concerned primarily with the simultaneous removal'f of' asphaltic materialsV and/or' color' imparting materials and one typeA of" hydrocarbon from. mixtures of: hydrocarbons containing' this type of hydrocarbon and asphalti'c` and/or colorimparting materials. The rst stage of my process involves intimately contacting the* di(beta cyano'etiIyl'amineV at suitable solventto oil ratios and temperatures with such petroleum products as crude oil cuts or: gas" oii. The contacting operation mayt be carried" out` continuously" a' counter'c'urrent contactingv tower, or' batch operation or by any other method' of contacting. The amine' solvent' dissolves' aromatic hydrocarbons and the asphaltic and/or color imparting; materials. The second stage in the operation involves" contacting4 of the extract" phase with'. a secondary solvent, such. as normal pentane", normal hexane, normal heptane, loW boiling napht-henes or. similar. hydrocarbons. ondary solvent extracts the aromatic: hydrocarbon trom-they extract phase andrejects the Iamine solvent as a secondary raffinate. The asphaltic materials and color' bodies remain in; the: amine?` phase. A third stage of my' process consists ini removing the asphalt-ic materialA and/or the color` producing. material fromV this amine phase- For: this separation step I prefer to recover a portion of the amine by vacuumzdistillation' of. the. aminephase and-,to recover thefremainderof the. amine.. by extraction of the vacuum still. bottoms with Water. The water and' the dissolved solventV may" then be easily separatedfrom the rejected onprecipitatedf. asphaltic. materials and. the solvent recovered from the Water by; distillation.. This method of amine recovery gives substantially complete'vrecoverycf the/primary solvent whereas by vacuumd distillation alonet the'y conditions forv .z

Thisv seo-f-v Sil' (Cl. 19d-44.15)`

substantially complete recovery of the solvent are so drastic that cracking' sets" in and causes considerable loss of the amine.

The gure illustrates diagrammatically one form of apparatus in which the process of my invention may be practiced".

The apparatus consists essentially of a liquidliquid contacting Vessel I2, a separator 24, a distillation means 39, a liquid-liquid contacter I6, a iiash tankl I8, a Vacuum stillV 28,-and a separator 36. These main pieces of apparatus are",l of course, connected with conduits for transfer off material in process from one point to another'. Several coolers or heat exchangers 45, 43, 33, 39 and 2| are provided for heating or coolingY material in process, as desired In the operation of thed process ofmy invention, the feed stock' to bel treated is conducted through a line II fromv a source, not shown', into contactor I2 at about a midpoint. Extraction liquid, i. e; di '-cyanoethyl) -amine,` is introduced into the column through pipe I'- at a point near the top. RaiiinateV phase, which is theV material-A Which is insoluble in the solvent, le'aves this vessel I2 at the topy and is conducted through* Di(beta-cy'anoethyl)` amine is miscible with Water in all proportions and accordingly, recovery' of theV amine from the raflinate maybe eiiected' merely' by addingV a sufficient amount' of Water from pipe I4 into the' raffinate phase flowing' in The hydrocarbon material from this r'aiiinateY phasethen rises to-the topl of the'separator' vessel 24- and may be removed fromthe process through conduit 2'5" as one product of the process. The Water solution of the amine' settles to the bottom of the separator' tank 24 and this solution may then bev transferred through pipe" 26 into the distillationmeans or vessel 39. A heating coil 4'I in vessel 39- supplies suiiicient heat for the distillation ofthe Water from the amine. The'separation of these two materials is not diilicult since there is considerable spread inY their" boiling points. Bubble caps or other efficient packing material are not needed in separator'39. However, it is preferable to insert a number' of balile's for' preventing loss ofy entrained amine inthe vaporous` water or steam leavingA the vessel through a conduit 40. The. amine free from Water thenIk may be withdrawn from the bottom of this vessel through pipe` 4I., cooled: in cooler` 45 'and'pas'sedvv on through` conduits 46' and 3| into line I and thence into the contactor vessel I2.

The extract phase is Withdrawn from vessel I2 through a line I5 and is passed into Vessel I5 at a point near the top thereof. For exemplary purposes I will describe this step of my process as employing normal pentane as the secondary solvent. This solvent is introduced into column I6 through a pipe 44 near the bottom of the column. In this contactor the upward rising liquid pentane extracts the aromatic hydrocarbons from the amine phase which flows downward. Extract from the operation passes through a line II into a flash tank I8 in which the normal pentane is ilashed overhead from the extracted aromatics. A heating coil I9 furnishes heat for this flashing step. The flashed pentane is passed through the pipe 42 and is condensed and cooled by condenser 43 While in transit to the extraction vessel I6. The aromatic-containing bottoms from the flash tank are withdrawn through pipe 20, cooled in cooler 2| andmay be Withdrawn from the system as the second product of the process through line 22. This product material 'may be passed to a storage tank or to other process step as desired. However, a portion of this aromatic material may be diverted from pipe 22 and passed through pipe 23 into the lower portion of the primary contacting vessel I2 to reflux the extract leaving vessel I2.

The rainatephase which accumulates in the bottom of the secondary contactor I6 is withdrawn therefrom and is passed through conduit 21 into a vacuum still 28 at about a midpoint. A connection leading from this vacuum still 28 to vacuum pumps is not shown for purposes of simplicity since the construction and operation of vacuum stills and vacuum producing equipment are well known. That portion of the amine vaporized in still 28 under high vacuum conditions is passed through the overhead line 29 and is condensed in condenser 30 to a liquid which is then passed by way of conduit 3| to be introduced into line I0 and thence into the primary contactor I2. The vacuum distilled bottoms which contains a considerable proportion of amine along with the asphaltic and/or color body material is passed through conduit 32, cooler 33 and on through conduit 34 to the separator 36 at about a midpoint. Liquid water from a source, not shown, is injected into this vacuum still bottoms through conduit 35. Sufficient water is added at this point to dissolve the amine and to precipitate the asphaltic and color body material. Since the asphaltic and color body material is precipitated as solid material, the separator 36 may include a filter press or decanter or other separating means whereby such material may be separated from the aqueous amine solution. Conduit 3'I is intended to be a means for the passage of the precipitated material from the separator to a storage tank or other disposal, as desired. The aqueous amine solution is passed from the separation means 36 through line 38 into the material in transit in pipe 26. The combined material is then passed into the distillation means 39, the operation of which has been discussed hereinbefore. The water originating from separator 36 and 24 (pipes I4 and 35) then passes through the conduit 40 to such disposal as desired while the amine leaves the separation means 39 through conduit 4I, is cooled in cooler 45 and passes on through conduits 45, 3l and I0 as recycle solvent to the primary extractor.

The primary extraction operation may be carried out at temperatures within the range of about 75 F. to 200 F., preferably between 100 F. and F. Pressure of this operation may be atmospheric or at a pressure sufficiently high to maintain all materials in process in the liquid phase. The secondary extraction step may be carried out at such pressure as Will be required to maintain the secondary solvent in the liquid phase. It will be obvious that when normal heptane is used as a secondary solvent, lower pressures may be used than when using normal pentane Vas the secondary solvent. Since normal pentane boils at about 99 F. suflicient pressure will need be maintained at this step to keep the pentane in liquid phase at all times.

The Vacuum still may be operated at a pressure within the approximate limits of 0.1 to 5 mm. The operation of this column is preferably such that from 20 to 90 per cent by weight, and more preferably 50 to 90 per cent, of the amine distills overhead. As mentioned hereinbefore, a substantial proportion of the amine should be permitted to remain in the liquid bottoms since if the bottoms are heated to a sufciently high temperature to take all the amine overhead, considerable decomposition of the amine occurs and, 'of course, such decomposition incurs loss of the primary solvent. The fractionator or separator 39 may be operated at a temperature between approximately 220 F. and 250 F. for removal of the Water from the amine. At this relatively low temperature decomposition of the amine does not take place.

One particular advantage of my process over prior art methods is that the asphaltic and color body material precipitated by the water from line 35 is easily and completely separated in separator 36. When diluting the entire quantity of solvent owing through line 2'I with water as in the prior art an emulsion Was produced from which asphalt and color body material Was not easily recovered. The emulsion appeared to be quite stable. Thus, by removing a portion of the di(beta-cyanoethy1) amine by vacuum distillation the remaining solution, I have found, is in condition for easy and complete asphalt precipitation by addition of water.

The extract phase in line I5 from the primary extractor contains extracted hydrocarbons, amine, and asphaltic and color body material and also forms an emulsion upon addition of water as above mentioned in relation to the solvent-asphalt-color body material flowing through line 2'I. Thus an emulsion is formed regardless of the extracted hydrocarbon content of the amine solu tion.

Specific example Primary Solvent-di (beta-cyanoethyl) amine Feed-thermally cracked gas oil having a furfural point of 204 F. and a carbon residue off 0.14%

Extraction temperature-140 F.

Pressure-atmospheric Solvent to oil ratio, by weight-2: 1

Primary rafnate-furfural point 217 F., carbon residue 0.14%

Secondary solvent-n-pentane Secondary extract-furfural point 28.4 F., carbon residue 0.52

Vacuum still-temperature F. at 2 mm. abs.

pressure, 75% of the amine in bottoms Vacuum still bottoms water added and asphaltic material recovered by filtration.

In the above described example, a thermally cracked gas oil having a furfura1 point of 204 F.

`was treated l.according -to .the process ,of my inven- .tion. The primary .solvent was =dibetacyano ethyD -zamine and the secondary solvent Was -nor- ;mal heptane. The primary raffinate recovered had =a furfural point .of 21.7 F. This furfural point 'was 13.higher than ,the furfural ,point ,of :the feed Astool: indicating that the paraiiinicity of this raiiinate product had been increased. The extract vfrom the secondary extraction operation `had a furfural point of 28,4 F. This :very .low zfurfuralpoint is, of course, an `indication of relatively high aromaticty. In the vacuum still step :for recovery fof the solvent 7.5% `of the amine was allowed to remain in the vbottoms Aand from this vbottoms Aproduct v.was recovered 'by precipita- `.tion :some asphaltic material which was recovered from the aqueous :amine :solution .by filtration.

Such auxiliary ,equipment as pumps, valves, temperature and .pressure measuringand record- :ing equipment, flow :meters vand flow controlling .equipment Yand the Alike .are not yshown lfor purposes 0f simplicity since :the .installationand use of such equipment is well understood "by those skilled in the art. It will be obvious that many variations and alterations in my process may be made, such as for example, .all or only a part of .the .aromatic material from the Vflash tank I8 m-ay be passed through conduit 22 as the product of the processor a part thereof may be recycled through the line 23 to Vreflux the extract leaving the primary contactor I2. The particular A'temperaturessof operationof ithe icontactors t2 and I6 Y'may .be fchosen Within the limits given depending upon .the .extracts .to `be `made and the ldegree o f :the .extractions desired. Also .the ratioy .of amine to the chargestock inthe primary contactor may be varied .for the Vparticular purpose at hand. Likewise vthe ratio of .the secondary solvent to the primary extract in .contacter LE Amay be varied depending .upon .the aextractiondesired.

It will be obvious to those skilled in the art that many variations and alterations in the operation of my process may be made and yet remain Within the intended spirit and scope of my invention.

Having disclosed my invention, I claim:

1. A process for the separation of one type of hydrocarbon and of asphaltic and color body material from a mixture containing these and another type of hydrocarbon as separate products comprising treating such a mixture of hydrocarbons with di(betacyanoethyl) -amine as a first selective solvent under conditions to form a first rafiinate phase and first extract phase, separating these phases, extracting with water the dissolved first solvent from the hydrocarbon of the first ranate phase and recovering this separated hydrocarbon free from said one type of hydrocarbon and asphaltic and color body materals as one product of the process; treating the first extract phase with a second selective solvent having a preferential selectivity for said one type of hydrocarbon under conditions to form a raffinate phase and an extract phase, separating this latter raffinate phase as the second raffinate phase and this latter extract phase as the second extract phase, separating said one type of hydrocarbon from the selective solvent of said second extract phase, recovering said separated one type of hydrocarbon as a second product of the process and recycling said separated selective solvent into the second treating step as said second selective solvent; vacuum distilling a portion of the dissolved first solvent from said second raihnate phase, extracting with Water the first solvent from the vacuum distillation bottoms and recovering 'this extraction residue Iasa separated asphaltic and c olor body third .product ofthe process; 4combining .the 'two .aqueous .solutions of first solvent, recovering solvent therefrom, adding the vacuum distilled rst Vsolvent and recycling :this combined first solvent :as `the iirstl selective solvent into the original treating step.

2. The process of claim 1 wherein the one'type of hydrocarbon separated is the aromatic v.type .o hydrocarbon.

3. YInrthe process .of claim .l wherein the second solvent is -a n-paraflinic hydrocarbon selected from Athe group .consisting of n-pentana nhexane, and An-heptane.

4. A .process `for the Aseparation 4of `one type ,of

:hydrocarbonand of asphaltic vand colorfbodyma'- terial from la mixture vcontaining these vand v`another -type *of .hydrocarbon .as separate .products comprising treating such :a mixture of .hydrocarbons .with di(betacyanoethyl)famine as .a first selective :solvent under conditions to form :a first raffinate phase andafirst extract phase, separa-t4 ing these ,ph-ases, extracting with water the .fdissolved first vsolvent from the hydrocarbon of said rstyraflinate phase and recovering this separated hydrocarbon `free from said ione type of hydro"- carbon and asphaltic and color body materialas one product of the process; `treating rsaid first extract phase with asecond selective solventihaving a .p1eferential selectivity. for :said 'one ltype hydrocarbon underconditions .to form a raffinate phase and an extract phase, separating .this la'tter rainate phase as thetsecond raflinate phase and this latter extract phaseias the-second extract phase, separating said one type of hydrocarbon from the selective solvent of .said second .extract phase, Arecovering said separated one 'type .of hydrocarbon as a second :product of the :process and recycling said sepa-ratedselective solvent into the second treating -step ras saidsecond Iselective solvent; vacuum distillng a .portionof' the dis'- solved first solvent from said second raffinate phase, extracting with water the first solvent from the vacuum distillation bottoms and recovering this extraction residue as the separated asphaltic and color body third product of the process; combining the two aqueous solutions of first solvent, recovering solvent therefrom, adding the vacuum distilled first solvent and recycling this combined first solvent as the first selective solvent into the original treating step, and recycling a portion of the recovered one type of hydrocarbon as reflux to the original treating step at a point near the point of Withdrawal of the first extract phase.

5. A process for the separation of one type of hydrocarbon and of asphaltic and color body material from a mixture containing these and another type of hydrocarbon as separate products comprising treating such a mixture of hydrocarbons with di(betacyanoethy1)-amine as a first selective solvent under conditions to form a first raiiinate phase and a first extract phase, separating these phases, extracting with Water the dissolved first solvent from the hydrocarbon of said first raffinate phase and recovering this separated hydrocarbon free from said one type of hydrocarbon and asphaltic and color body material as one product of the process; treating said first extract phase with a second selective solvent having a preferential selectivity for said one type hydrocarbon under conditions to form a raffinate phase andan extract phase, separating this latter rafiinate phase as the second raiiinate phase and this latter extract phase as the second extract phase, separating said one type of hydrocarbon from the selective solvent of said second extract phase, recovering said separated one type of hydrocarbon as a second product of the process and recycling said separated selective solvent into the second treating step as said second selective solvent; vacuum distilling a portion of the dissolved rst solvent from said second raiinate phase, extracting with water the first solvent from the vacuum distillation bottoms and recovering this extraction residue as a separated asphaltic and color body third product of the process; combining the two aqueous solutions of rst solvent, recovering solvent therefrom, adding the vacuum distilled rst solvent and recycling this combined rst solvent as the rst selective solvent into the original treating step, and operating the rst extraction step between the temperature limits of 75 and 200 F. and the second extraction step between the temperature limits of 50 and 200 F.

6. A process for the separation of one type of hydrocarbon and of asphaltic and color body material from a mixture containing these and another type of hydrocarbon as separate products comprising treating such a mixture of hydrocarbons with di(betacyanoethyl) -amine as a rst selective solvent under conditions to form a rst raffinate phase and a rst extract phase, separating these phases, extracting with Water the dissolved rst solvent from the hydrocarbon of said rst ranate phase and recovering this separated hydrocarbon free from said one type of hydrocarbon and asphaltic and color body material as one product of the process; treating said rst extract phase with a second selective solvent having a preferential selectivity for said one type hydrocarbon under conditions to form a rafnate phase and an extract phase, separating this latter raffinate phase as the second rafnate phase and this latter extract phase as the second extract phase, separating said one type of hydrocarbon from the selective solvent 8 of said second extract phase, recovering said separated one type of hydrocarbon as a second product of the process and recycling said separated selective solvent into the second treating step as said second selective solvent; vacuum distilling a portion of the dissolved rst solvent from said second ralnate phase, 'extracting With Water the rst solvent from the vacuum distillation bottoms and recovering this extraction residue as a separated asphaltic and color body third product of the process; combining the two aqueous solutions of rst solvent, recovering solvent therefrom, adding the vacuum distilled rst solvent and recycling this combined first solvent as the first selective solvent into the original treating step, and wherein the secondary solventis such a hydrocarbon as will selectively dissolve said one class of hydrocarbon to the exclusion of said iirst selective solvent and the asphaltic and color body material, and operating the first and second extraction steps between the temperature limits of to 200 F., and 50 to 200 F., respectively.

HERBERT R. ANTLE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

1. A PROCESS FOR THE SEPARATION OF ONE TYPE OF HYDROCARBON AND OF ASPHALTIC AND COLOR BODY MATERIAL FROM A MIXTURE CONTAINING THESE AND ANOTHER TYPE OF HYDROCARBON AS SEPARATE PRODUCTS COMPRISING TREATING SUCH A MIXTURE OF HYDROCARBONS WITH DI(BETA-CYANOETHYL)-AMINE AS A FIRST SELECTIVE SOLVENT UNDER CONDITIONS TO FORM A FIRST RAFFINATE PHASE AND FIRST EXTACT PHASE. SEPARATING THESE PHASES, EXTRACTING WITH WATER THE DISSOLVED FIRST SOLVENT FROM THE HYDROCARBON OF THE FIRST RAFFINATE PHASE AND RECOVERING THIS SEPARATED HYDROCARBON FREE FROM SAID ONE TYPE OF HYDROCARBON AND ASPHALTIC AND COLOR BODY MATERIALS AS ONE PRODUCT OF THE PROCESS; TREATING THE FIRST EXTRACT PHASE WITH A SECOND SELECTIVITY SOLVENT HAVING A PREFERENTIAL SELECTIVELY FOR SAID ONE TYPE OF HYDROCARBON UNDER CONDITIONS TO FORM A RAFFINATE PHASE AND AN EXTRACT PHASE, SEPARATING THIS LETTER RAFFINATE PHASE AS THE SECOND RAFFINATE PHASE AND THIS LETTER EXTRACT PHASE ASS THE SECOND EXTRACT PHASE, SEPARATING SAID ONE TYPE OF HYDROCRBON FROM THE SELECTIVE SOLVENT OF SAID SECOND EXTRACT PHASE, RECOVERING SAID SEPARATED ONE TYPE OF HYDROCARBON AS A SECOND PRODUCT OF THE PROCESS AND RECYCLING SAID SEPARATED SELECTIVE SOLVENT INTO THE SECOND TREATING STEP AS SAID SECOND SELECTIVE SOLVENT; VACUUM DISTILLING A PORTION OF THE DISSOLVED FIRST SOLVENT FROM SAID SECOND RAFFINATE PHASE, EXTRACTING WITH WATER THE FIRST SOLVENT FROM THE VACUUM DISTILLATION BOTTOMS AND RECOVERING THIS EXTRACTION WITH WATER THE FIRST ASPHALTIC AND COLOR BODY THIRD PRODUCT OF THE PROCESS; COMBINING THE TWO AQUEOUS SOLUTIONS OF FIRST SOLVENT, RECOVERING SOLVENT THEREFROM, ADDING THE VACUUM DISTILLED FIRST SOLVENT AND RECYCLING THIS COMBINED FIRST SOLVENT AS THE FIRST SELECTIVE SOLVENT INTO THE ORIGINAL TREATING STEP. 